Voltammetric Determination of Lidocaine and Its Toxic Metabolite in Pharmaceutical Formulation and Milk Using Carbon Paste Electrode Modified with C18 Silica

Abstract

A new voltammetric method was developed for simultaneous determination of lidocaine hydrochloride (LH) and its toxic metabolite (2, 6-dimethylaniline (DMA)) based on their oxidation and adsorption on C18 silica modified carbon paste electrode (SMCPE). Several experimental factors including the effect of pH, scan rate, percentage of silica, accumulation potential and time were studied and the optimum conditions were found to be: pH 11 ± 0.10 using Britton Robinson buffer, 100 mV/s scanning rate, −0.6V accumulation potential, 150 s accumulation time and 5% C18 silica. Under the optimized conditions, applying square wave voltammetry (SWV) displayed two signals for DMA and LH at 0.56 and 0.87 V, respectively. The method revealed satisfactory results in terms of linearity (7.94 × 10−6 to 1.07 × 10−4 M) for LH and (1.20 × 10−6 to 1.07 × 10−5 M) for DMA, accuracy, and precision. The limit of detection was found to be 2.19 × 10−6 and 2.15 × 10−7 M for LH and DMA in pure forms, respectively. The developed SWV method was further applied for the assay of LH in its pharmaceutical dosage form and DMA in spiked milk samples.